Touchscreen interfaces which enable a user to interact with a computer display, terminal, etc. are found in many applications. In a touchscreen-type apparatus, the user touches areas of a video screen with his or her finger in order to activate control functions displayed on the video screen, to select a menu item from list of items displayed on the video screen, etc. In one type of touchscreen technology, the location on the video screen contacted by the user is detected using an array of emitters and associated detectors positioned along the perimeter of the video screen. In most, if not all applications, the video screen perimeter is square or rectangular. Emitters are positioned along one vertical and one horizontal side of the perimeter, and the corresponding detectors are positioned on the opposite vertical and horizontal sides across from and in alignment with an associated emitter. With this arrangement, the touchscreen is divided into multiple touch zones, the number of zones being determined by the number of emitter/detectorpairs. For example, if four vertical emitter/detectorpairs and four horizontal emitter/detectorpairs are used, the video screen is divided into a matrix of 16 zones. The position touched by a user is determined by which horizontal and vertical beam paths are blocked by the user's finger.
In explosive environments, data display terminals and/or instrumentation must be contained within explosion-proof housings. Data entry devices enabling an operator to interact with instrumentation, data terminals, etc. that are located in an explosion-proof environment are not readily available, and what is available can be extremely costly. In many hazardous environments, interacting with process instrumentation and controls is done in a secured control room environment that is sealed and isolated from the process environment. In order to interact with or access process instrumentation and controls, the operator must leave the process environment and enter the isolated control room.
It has been found desirable for some applications to be able to access and interact with terminals and other instrumentation located in the process environment. For example, being able to interact with a display terminal on the process floor in order to display process parameters and/otto change process parameters would enable an operator to more quickly modify process conditions because it would obviate the need for leaving the processing environment to enter a separate control room. Apparatus enabling an operator to directly interact with instrumentation contained within an explosion-proof housing, is not readily available, and what is available is considered to be prohibitively expensive for many applications.
It is also desirable in some applications to be able to transmit a signal across a barrier which at least partially defines an explosion-proof room or enclosure. In this type of signal transmission it is not necessary that an operator be able to interact with the signal. However, it is very important that signal quality and integrity be maintained during the transmission.